1. Field
This invention pertains to the field of intraocular devices and procedures, and more particularly, a capsular ring for strengthening a capsular bag, for holding open a capsular bag of an eye, and/or for providing accommodation.
2. Description
A human eye can suffer diseases that impair a person's vision. For instance, a cataract may increase the opacity of the lens, causing impaired vision or blindness. To restore the patient's vision, the diseased lens may be surgically removed and replaced with an artificial lens, known as an intraocular lens, or IOL. An IOL may also be used for presbyopic lens exchange.
The simplest IOLs have a single fixed focal length, or, equivalently, a single fixed power. Unlike the eye's natural lens, which can adjust its focal length and/or axial location within a particular range in a process known as accommodation, these single focal length IOLs cannot generally accommodate. As a result, distant objects may appear in focus, while objects at closer distances appear blurred.
An improvement over fixed, single focal length IOLs is an accommodating IOL, which can move axially and/or adjust its optical power within a particular range. As a result, the patient can clearly focus on objects in a range of distances away from the eye, rather than at a single distance. This ability to accommodate is of tremendous benefit for the patient, and more closely approximates the patient's natural vision than a single focal length IOL.
When the eye focuses on a relatively distant object, the lens power is at the low end of the accommodation range, which may be referred to as the “distant” or “far” power. When the eye focuses on a relatively close object, the lens power and/or position is at the high end of the accommodation range, which may be referred to as the “near” power. The accommodation range or add power is defined as the actual or effective near power minus the far power. In general, an accommodation range of 2 to 4 diopters is considered sufficient for most patients.
The human eye contains a structure known as the capsular bag, which surrounds the natural lens. The capsular bag is transparent, and serves to hold the lens. In the natural eye, accommodation is initiated by the ciliary muscle and a series of zonular fibers, also known as zonules. The zonules are located in a relatively thick band mostly around the equator of the lens, and impart a largely radial force to the capsular bag that can alter the shape and/or the location of the natural lens and thereby change its actual or effective power.
In a surgery in which the natural lens is removed from the eye, a small opening is made in the front of the capsular bag through which lens material is typically broken up and vacuumed out of the eye, the rest of the capsular bag being left intact. The remaining capsular bag is extremely useful for an accommodating intraocular lens, in that the eye's natural accommodation is initiated at least in part by the ciliary muscle and the zonules through the capsular bag. The capsular bag may be used to house an accommodating IOL, which in turn can change shape and/or shift in some manner to affect the power and/or the axial location of the IOL.
In general, the IOL includes an optic, which refracts and/or diffracts light that passes through it and forms an image on the retina, and a haptic, which mechanically couples the optic to the capsular bag. During accommodation, the zonules exert a force on the capsular bag, which in turn exerts a force on the optic. The force may be transmitted from the capsular bag directly to the optic, or from the capsular bag through a haptic to the optic.
A desirable optic for an accommodating IOL is one that changes shape or axially moves in response to a squeezing or expanding radial force applied largely to the equator of the optic (e.g., by pushing or pulling on or near the edge of the optic, circumferentially around the optic axis). Under the influence of a squeezing force, the optic bulges slightly in the axial direction, producing more steeply curved anterior and/or posterior faces, and producing an increase in the power of the optic. Likewise, an expanding radial force may produce a decrease in the optic power by flattening the optic. This change in power is accomplished in a manner similar to that of the natural eye and is well adapted to accommodation. Furthermore, this method of changing the lens power reduces any undesirable pressures exerted on some of the structures in the eye.
One challenge in replacing a natural lens with an IOL is to keep the capsular bag intact and to prevent the capsular bag from tearing or collapsing after the natural lens is removed from the eye so that the IOL can be implanted and properly positioned in the capsular bag. This problem can be exacerbated by the relatively large (e.g., 4 mm) incision that is typically required for this procedure. Since the zonules are attached both above and below the equator of the capsular bag, keeping the bag open offers potential for more effectively utilizing accommodative forces on the IOL.
Accordingly, it would be desirable to provide a device for facilitating the insertion elan intraocular lens into a capsular bag of an eye. It would also be desirable to provide such a device that can accommodate and hold an intraocular lens in the capsular bag.
In one aspect of the invention, a device includes a plurality of ringlets connected together to form a ring having a longitudinal axis. Each ringlet comprises a first element and a second element. The first and second elements each extend from a first end thereof through a central portion thereof to a second end thereof. The first and second ends of each element are disposed at radially outer positions with respect to the ring than the central portion of the element. The central portion of each element is longitudinally displaced from the first and second ends thereof. The first and second elements are separated and spaced apart from each other at the central portions thereof, and are joined together at the first ends thereof and the second ends thereof. The ringlets are connected together such that the first ends of the elements of one ringlet are connected to the second ends of the elements of an adjacent ringlet.
In another aspect of the invention, a device is provided for implantation into a capsular bag of an eye. The device comprises a ring element adapted to be inserted through an incision in the capsular bag and to hold open the capsular bag; and an optic adapted to be inserted into the capsular bag having the ring inserted therein, and to be operatively engaged with the ring so as to be held within the capsular bag. The ring element has a longitudinal axis and comprises a plurality of ringlets connected together. Each ringlet comprises a first element and a second element. The first and second elements each extend from a first end thereof through a central portion thereof to a second end thereof. The first and second ends of each element are disposed at radially outer positions with respect to the ring than the central portion of the element. The central portion of each element is longitudinally displaced from the first and second ends thereof. The first and second elements are separated and spaced apart from each other at the central portions thereof, and are joined together at the first ends thereof and the second ends thereof. The ringlets are connected together such that the first ends of the elements of one ringlet are connected to the second ends of the elements of an adjacent ringlet.